Not a dig at you Homer, but I've never understood that saying.
Surely the engine of the whole unit is the golfer as he provides the power.
I would, in this instance, liken the shaft to the gearbox transmitting the power to the ball.
You could put the gear box from a Robin Reliant in a BMW, but I bet it wouldn't work properly![]()
But with an incorrect shaft the swing is always going to have to compensate. I had a set of TM Burner woods (off the shelf) all supposedly R flex. The driver felt more rigid than the S flex, the 5 wood was like wet spaghetti and the three wood was the only one that I really trusted. I accept that a flawed swing will have an impact on the strike/direction but I still think the shaft has a big impact.
I swung Nick Faldo's 8 iron. It was like a scaffold pole and even a reasonably easy to hit mid iron lie that was uncontrollable for me